Optical projection apparatus



Jan. 28, 1947. G. H. REID ETAL 2,414,977

OPTICAL PROJECTION APPARATUS Filed Feb. 27, 1945 3 Sheets-Sheet l flit/Bionic Jan. 28, 1947. G. H. REID ETAL 2,414,977

ornmu, PROJECTION APPARATUS Filed Feb. 2'7, 1945 3 Sheets-Sheet 2 I Mad-awe;

w Attorneys Jan. 28, 1947.

G. H. REID ETAL OPTICAL PROJECTION APPARATUS 5 Shets-Sheet 3 Filed Feb. 27, 1945 MW Attorneys Patented Jan. 28, 1947 GPTHJAL PROJECTION APPARATUS George Hancock Reid, Kirby Muxloe, near Leicester, and Leicester Gordon Heath Cantle, St. Marks Hill, Surbiton, England, assignors to Reid and Sigrist Limited, Kirby Muxloe, near Leicester, England Application February 27 1945, Serial No. 579,938 In Great Britain October 7, 1943 (Q1. ss24) 1 Claim. 1

This invention relates to optical projection apparatus of the kind used for projecting an enlarged image of an opaque object on to a screen by means of an objective lens for the purpose of inspection or measurement.

It is well known that in optical projectors of the above kind the enlarged image of the object is projected on to the screen forming part of the casing of the projector. The source of light is enclosed in a box which keeps in all the light except that which forms the image on the screen. The emitted light passes through a magnifying lens system or objective lens on to the screen. v It is also known that an optical projector of the above kind may be used to project either the image of an illuminated surface of the object or the silhouette of the object.

It is an object of the present invention to provide an improved optical projector of the above kind which is arranged so that both the object and the objective lens can be quickly and easily changed.

According to a feature of the present invention an optical projector comprising a source of light and an objective lens system for projecting an image of an opaque object on to a screen is provided with a rotatable disc or like member'for supporting a p urality of objects, and a second rotatable member or turret supporting a plurality of objective lenses, said rotatable members being arranged so that any one of the objects may be brought into operative relatio-nship'with any one of the objective lenses and with a source of light.

According to a further feature of the invention an optical projector comprises a source of light and an objective lens for projecting an image of an opaque object on to a screen is provided with lever mechanism for adjusting the position of the object relative to the objective lens so that the image of the object can be focussed.

Preferab y the apparatus is arranged so that either an illuminated surface or the silhouette of the object may be projected on to the screen,

According to a further feature of the invention an optical projector comprising a lamp box containing a source of light for illuminating the surface of an object and an objective lens system for projecting an image of said illuminated surface on to a screen, is provided with ventilating means for permitting the circulation of air through said 7 lamp box without allowing the passage of light through said means.

According to a further feature of the invention an optical projector comprises a source of light, an objective lens system and an adjustably mounted reflector for projecting an image of an opaque bject on to a screen.

Referring to the accompanying drawings:

Figure 1 is a side elevation in section of an optical projector according to this invention;

Figure 2 is a front elevation of the apparatus partly in section-on theline II-II in Figure 1;

Figure 3 is a plan of the apparatus;

Figure 4 is a detail view in plan; and

Figure 5 is a side elevation of Figure l.

A sheet metal casing ll! carries in its upper portion a rigid'frame l2 which supports a rotatable disc M on which a number of objects or specimens can be mounted and a rotatable turret l6 carrying a number of objective lenses of different focal length. Surmounting the frame I2 is a lamp house H3 in which a lamp 2!] and a condensing lens 22 for illuminating the objects or specimens carried by the rotatable disc l4 when these are to be projected in silhouette. Within the casing are two lamp housings 24 each having a lamp 2B and a condenser lens 28 for illuminating the underside of objects to be projected under surface illumination. One or other of the objective lenses 3!! carried by the turret I6 projects an image of one of the objects on to a translucent screen 32 in the front part of the top of the easing II], the light being reflected upwardly and forwardly by a mirror 34 adjustably mounted in the bottom of the casing Ill and the translucent screen 32 being suitably inclined as shown in Figure 1 so that the image formed by the objective lens 39 is in focus throughout the area of the screen. The various objective lenses are arranged at different heights as clearly shown in Figure 1 in accordance with their varying focal lengths. It is, however, necessary to provide an adjustment for bringing the projected images of the various objects into correct focus on the screen 32 and it is effected, as will be described hereinafter, by a vertical movement of the disc 14.

This disc is secured to the upper end of a vertical spindle 36 mounted to rotate and slide in bearings 38. Secured to the spindle 36 is a collar 40 which rests upon the outer races of two ball bearings 42 serving as rollers, these rollers being carried at one end of a forked lever 44 (Figure 2) centrally pivoted at 45 to a bracket 48 carried by the frame l2. The other end of vthe lever carries another pair of ball-bearing rollers 50 bearing against the underside of a nut 5| through which extends a vertical screw-threaded spindle 52. This spindle is carried in an upper bearing 54 at the top of the casing l9 and a lower bearing 56 in a plate 53 secured to the lower end of a vertical l l l s guide-rod 60. This guide-rod is secured ai its upper end in a plate 62 fixed in the top of the asing it and also carrying the bearing 54. A guide sleeve 64 slides on the guide-rod 68 and is fixed to the nut by means of lugs 66. Thus the nut 5! is held against rotation and guided in a vertical path.

The upper end of the spindle 52 carries a hand-wheel 68 by which the spindle can be rotated to cause the nut 55 to travel up or down, the motion of the nut being communicated without backlash to the spindle 36 which carries the disc M on which objects to be examined are mounted. Thus the image on the screen 32 of any of these objects can be brought into sharp focus, whichever of the objective lenses 5% is in use.

{The disc l4 overlaps the turret It as shown inFigure 5. By rotating the disc l4 and the turret iii any one of the lenses 3H and any one of the apertures can be brought into alignment with the condensing lens 22 so that light from the lamp 2!! passes through the aperture ill, the lens 39 and an aperture 12 in the frame l2 on its way to the mirror 34. The disc M is provided with a number of radially disposed clamping devices is, one for each aperture 19, by means of which objects to be inspected can be clamped to the disc immediately above the aperture it.

There are four objective lenses 36 arranged at intervals of 90 as shown in Figure t and the turret It is formed with four holes 15 at the corners of a square with the axes of the four lenses 3!! at the mid points of the sides of the square. It will be apparent, therefore, from a. comparison of Figures 1, 4 and 5 that when any one of the objective lenses 3% is in alignment with the condensing lens 22 it will be flanked by two of the holes 16 the centres of which are situated on a line perpendicular to the paper. These two holes allow light from the lamps EC. to shine upon the underside of an object carried by the plate M When an object is thus illuminated (the lamp 26 being extinguished) an image of the surface of the object is visible upon the screen 32,

The lamp 2!} is surmounted by a concave mirror 2i and is situated in a lamp housing 12 formed with external ribs to facilitate the dissipation of heat from the housing. An air outlet 2? is provided in the top of the housing i8 and this outlet is surmounted by a metal plate 23 flanged downwardly at its margin to minimise the escape of light from the housing.

The condensing lens 22 is mounted in the lower side of the housing [8, which is supported on a pair of horizontal bars 3'! carried by standards 33 secured to the top of the casing H).

The lower end of each of the lamp housings 24 is formed with a ring of holes 35' for the admission of air, hot air escaping through exhaust conduits 37 discharging the heated air outside the casing I0. Attached to the lower end of the lamp housing is a cup-shaped light trap 39' which is spaced away from the sides of the housing and thus allows air to enter the housing through the holes 35 while preventing the escape of light through these holes. Each lamp housing 24 is provided with an arm 41 secured in a clamp at the lower end of a rod' 45 carried by a lug ll adjustably mounted in a bracket 49 secured to \the inside of the top of the casing It. By these means the lamp housings can be adjusted angujlarly so that the light from the lamps 25 focussed by the condensers 28 can be directed upon the underside of the object carried by the disc I l when this object is in alignment with the condensing lens 22 and the objective lens 3!] in use.

I The turret I6 is secured to a spindle 53 mounted to rotate in a bearing sleeve 55 carried by the frame l2. The spindle carries a thrust collar 5! which rests on the upper end of the bearing sleeve 55. The spindle extends upwardly from the turret i6 and is formed at its upper end with a knob 59 by means of which the turret can be manually rotated. The lower end of the spindle extends downwardly through the lower member of the frame I2 in which it is mounted in a ball bearing El and terminates in a collar or bush 63. A spring 55 is provided between the collar or bush 63 and the ball bearing iii to maintain the spindle and supporting disc resiliently in position on the vertical bearing.

The mirror 34 is hinged to a supporting frame 6'? which can be raised or lowered by means of screws 89 attached to the base plate H of the casing 29. The angle between the mirror 34 and the supporting frame 61 can be adjusted by means of a fine pitch screw 73.

The casing is is provided at the front with a compartment '55 within which is a rack :"i for spare parts of the apparatus such as lenses, lamps and the like. The screen 32 may be marked with scale divisions and the like in known manner,

What we claim is:

Optical projection apparatus comprising a rotatable disc provided with a plurality of spaced translucent areas equidistant from the axis oi rotation, means for supporting objects in said areas for image projection, a light source lcca' above said disc, a condenser lens system for focussing light from said source on one portion of said disc that lies the same distance from its of rotation as the translucent areas so that by rotation of the disc any of the objects may be lighted from said source a second. lig' t source located below said disc, a second ccnde r le s system for iocussing the light from said second source on said one portion of said disc, a rotetable lens turret located between said disc and said second ,condenser lens system. plurality of objective lenses mounted on said turret for selective vertical registry with said one portion of said disc, said turret having a translucent portion so located with respect to each lens to register with the light path between said condenser system and, said ole portion oi said disc when the respective lens is in vertical registry with said one portion of said disc, a viewing screen, means for directing the light passing through the objective lens to said screen, a shaft supporting said disc for rotation, a thrust collar on said shaft, a lever, means for pivotally sup-- porting said lever intermediate its ends. one d of the lever bearing upwards against the tin collar, and screw driven means pressing the other end of the lever downwards to raise the shaft and disc.

GEORGE FANCOCK REID. LEICESTER GORDON HEATH CANTLE. 

